Department of Microbiology & Immunology
University of Illinois

How proteins "thread" back and forth across membranes is a key question in understanding structure and, therefore, function. When a single positively charged amino acid in the sequence is removed or added, the two ends of leader-peptidase switch from the outside surface of the cell membrane to the inside surface, thus flipping the protein entirely. Fusing alkaline phosphatase into short hydrophilic regions of the maltose transport protein allows mapping of which segments were on the inside and which on the outside.

I. Nilsson, G. von Heijne, "Fine-tuning the topology of a polytopic membrane protein: role of positively and negatively charged amino acids," Cell, 62, 1135-41, 21 September 1990. (Karolinska Institute, Huddinge, Sweden) M. Ehrmann, D. Boyd, J. Beckwith, "Genetic analysis of membrane protein topology by a sandwich gene fusion approach," Proceedings of the National Academy of Sciences (PNAS), 87...

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